Dual-side wafer bar grinding

ABSTRACT

A dual-side wafer bar grinding method and apparatus is disclosed herein that slices wafer bars from a wafer block for use in manufacturing thin film magnetic heads, for example. By grinding opposing faces of the wafer bars sliced from the wafer block, variations in flatness, perpendicularity, surface finish, and/or overall dimensions are improved.

BACKGROUND

Semiconductor device fabrication techniques may be used to create thin film heads (or magnetic heads) used in hard disk drive manufacturing and other electronic devices. These techniques may include various mechanical, photolithographic, and chemical processing steps during which a thin film head for reading data from and/or writing data to a disk media is created on a thin film wafer (e.g., an aluminum titanium carbide (AlTiC) wafer). Various machining processes are applied to the thin film wafer to form an individual thin film head.

One of the aforementioned processing steps is thin film wafer slicing. Wafer slicing involves cutting a wafer block into bars or strips of wafer material (wafer bars) using a rotating slicing blade. Each bar of wafer material includes a row of thin film heads. In order to maximize the number of heads that may be generated from a single wafer, the thickness of the slicing blade is minimized (e.g., it may be less than 50 μm thick). However, as the slicing blade thickness is reduced, the slicing blade becomes more flexible. Flexing of the slicing blade while slicing wafer bars can cause variations in flatness, perpendicularity, surface finish, and/or overall dimensions of the sliced wafer bars.

Another of the aforementioned processing steps, wafer grinding, is used to address the variations in flatness, perpendicularity, surface finish, and/or overall dimensions of the sliced wafer bars. After a first wafer bar is sliced from the wafer block, a grinding wheel grinds the exposed surface of the next wafer bar before it is sliced from the wafer block. These steps may iteratively repeat until no additional bars can be sliced from the wafer block. Typically, the air-bearing surface (ABS) of the wafer bars is the ground surface and the opposing sliced surface does not get ground.

This one-sided wafer grinding process partially addresses the variations in flatness, perpendicularity, surface finish, and/or overall dimensions of the sliced wafer bars, but not fully. For one, applying the wafer grinding process to one surface of a wafer bar, but not the opposite wafer bar surface may cause the wafer bar to bend due to the differing machining processes applied to the wafer bar, which creates different stresses on the two sides of the wafer bar. This further affects the flatness, perpendicularity, surface finish, and/or overall dimensions of the sliced wafer bars. Further, the non-ground surface of the wafer bars requires substantially more additional surface processing (e.g., lapping) than the ground surface of the wafer bars if both surfaces have similar flatness, surface finish, and/or overall dimensional requirements.

SUMMARY

Implementations described and claimed herein address the foregoing problems by providing a method comprising grinding opposing faces of a wafer bar sliced from a thin film wafer block.

Implementations described and claimed herein further address the foregoing problems by providing an apparatus comprising a slicing blade mounted on an axle that slices wafer bars from a thin film wafer block and a grinding wheel mounted on the axle that grinds opposing faces of the wafer bar.

Implementations described and claimed herein still further address the foregoing problems by providing a bar of thin film heads sliced from a block of substrate material, wherein the bar of thin film heads has mechanically ground opposing faces.

Other implementations are also described and recited herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example dual-side wafer grinding apparatus.

FIG. 2 is a side view of an example dual-side wafer grinding apparatus during a slicing operation.

FIG. 3 is a side view of an example dual-side wafer grinding apparatus during a first grinding operation.

FIG. 4 is a side view of an example dual-side wafer grinding apparatus during a second grinding operation.

FIG. 5 is a side view of an example dual-side wafer grinding apparatus during a simultaneous dual grinding operation.

FIG. 6 is a perspective view of a wafer block and a dual-side ground wafer bar.

FIG. 7A is a partial cross-sectional view of a dual-side grinding wheel with a rounded cutting surface.

FIG. 7B is a partial cross-sectional view of a dual-side grinding wheel with a squared cutting surface.

FIG. 8 is a front partial view of an example slicing/grinding assembly with a dual-side wafer grinding wheel.

FIG. 9 illustrates example operations for operating a dual-side wafer grinding apparatus to manufacture wafer bars.

DETAILED DESCRIPTIONS

A dual-side wafer grinding process that addresses variations in flatness, perpendicularity, surface finish, and/or overall dimensions of a sliced wafer bar without introducing significantly different forces on each of the sliced surfaces of the wafer bar is disclosed herein. In various implementations, maximum tolerances may be applied to the flatness, the perpendicularity, the surface finish, and/or the overall dimensions of each sliced wafer bar to achieve a desired wafer bar quality.

Flatness refers to a relative measurement of all elements on a surface residing in a singular plane. In one implementation, the relative measurement of flatness is a maximum linear variation from the planar surface in the form of a protrusion or a recession from the planar surface. Flatness may be measured with reference to either or both of the sliced surfaces of the wafer bar. Perpendicularity refers to a measurement of variation of two planar surfaces (e.g., both sliced surfaces of the wafer bar) from a normal condition with respect to one another. In one implementation, the two planar surfaces refer to a sliced surface of the wafer block and a back side of the wafer block. In another implementation, the two planar surfaces refer to both sliced surfaces of the wafer bar. In various implementations, perpendicularity is measured in the form of an angle or a quantity. Surface finish refers to a relative measurement of finely spaced surface irregularities, which are inherent to the slicing and/or grinding operations disclosed herein.

FIG. 1 is a perspective view of an example dual-side wafer grinding apparatus 100. The apparatus 100 includes a jig 102 and a slicing/grinding assembly 104. The jig 102 includes a jig base 105 that is moveable at least in the x-direction with precision. Further, the jig base 105 may also be rotatable in the x-y plane with precision. The jig base 105 is used to orient a wafer block 106 with respect to the slicing/grinding assembly 104. A translation stage 108 is mounted on the jig base 105 and is moveable in the y-direction on rails (not shown) with precision (as illustrated by arrow 112). The translation stage 108 is used to move the wafer block 106 into and out of position for the slicing/grinding assembly 104 to accurately slice wafer bars (not shown) from the wafer block 106 and grind the sliced surfaces of the wafer bars and the wafer block 106. The translation stage 108 is depicted in FIG. 1 in position for slicing operations.

The wafer block 106, which is bonded an extender 110, and a pusher 112 are all mounted on the translation stage 108. The extender 110 provides a structure to be held within the jig 102 while the wafer block 106 is sliced. Since the wafer block 106 to a size insufficient to securely hold within the jig 102, directly holding the wafer block 106 may be impractical. Further, the wafer block 106, the extender 110, and the pusher 112 are moveable as a unit in the y-direction, but substantially fixed in the x-direction and the z-direction with respect to the translation stage 108. The pusher 112 includes a handle or extension that carries an applied y-direction force (as illustrated by arrow 114) to the extender 110. The extender 110 receives the y-direction force and carries it to the wafer block 106. The extender 110 may be bonded to the wafer block 106 to provide a solid work piece. The wafer block 106 is a block of substrate material (e.g., AlTiC) from which the apparatus 100 precisely slices individual wafer bars. In some implementations, the substrate material is crystalline. In other implementations, the substrate material is semiconducting or insulating.

In an example implementation, the translation stage 108 starts in a position against a stop on the base 105, as shown in FIG. 1. The wafer block 106/extender 110/pusher 112 assembly is then loaded into the apparatus 100 on top of the translation stage 108. The y-direction force is applied to the pusher 112 to move the wafer block 106 to a desired position (e.g., in contact with a rotating stop (or flipper) 115).

Once the wafer block 106 is in the desired position, a vacuum is applied to a bottom surface of the wafer block 106 and the extender 110 via apertures or channels (not shown) in the translation stage 108 to hold the wafer block 106 and the extender 110 in the desired position (referred to herein as a vacuum chuck). Further, a vacuum is also applied to the face of the wafer block 106 in contact with the rotating stop 115 via apertures or channels (not shown) in the rotating stop 115. In some implementations, mechanical clamps (not shown) may supplement or be used instead of the vacuum on the translation stage 108. As a result, the wafer block 106 is securely held in the desired position without change during slicing and/or grinding operations. Once the wafer block 106 is securely held in the desired position, the pusher 112 may be retracted. Wafer alignment may then be performed by adjusting the x-y plane rotation (e.g., +/−5 degrees) of the jig 102 based on alignment marks (not shown) on the wafer block 106 through an optical vision system, for example.

The slicing/grinding assembly 104 includes an axle or spindle shaft 118 that rotates about axis 120 as illustrated by arrow 122. Both the slicing blade 116 and a grinding wheel 124 are mounted on the spindle shaft 118 and also rotate about axis 120. In one implementation, the slicing blade 116 is a diamond abrasive wheel. Further, an outer diameter of the grinding wheel 124 may be smaller than an outer diameter of the slicing blade 116 in order to prevent the grinding wheel 124 from contacting the apparatus 100 when the slicing blade 116 is being used. In implementations where the respective orientations of the slicing blade 116 and the grinding wheel 124 are reversed, the outer diameter of the slicing blade 116 may be smaller than the outer diameter of the grinding wheel 124.

FIG. 2 is a side view of an example dual-side wafer grinding apparatus 200 during a slicing operation. The apparatus 200 includes a jig 202 and a slicing/grinding assembly 204. The jig 202 includes a jig base 205 used to orient a wafer block 206 with respect to the slicing/grinding assembly 204. In one implementation, the jig base 205 is oriented in a fixed position in the y-direction. The rotating stop 215 controls the wafer block 206 position in the y-direction by contact with the rotating stop 215. The slicing/grinding assembly 204 is moveable in the y-direction with precision to control the slicing location on the wafer block 206. As a result, the slicing/grinding assembly 204 can precisely control wafer bar 230 thickness. A translation stage 208 is mounted on the jig base 205 and is moveable in the y-direction on rails (not shown) with precision (as illustrated by arrow 212). The translation stage 208 is used to move the wafer block 206 into and out of position for the slicing/grinding assembly 204 to accurately slice the wafer bar 230 from the wafer block 206 and grind the sliced surfaces of the wafer bar 230 and the wafer block 206. The translation stage 208 is depicted in FIG. 2 in position for slicing operations.

The wafer block 206 is placed in a desired position in contact with the translation stage 208 and the rotating stop 215. A vacuum is applied to a bottom surface of the wafer block 206 via apertures or channels (not shown) in the translation stage 208 to hold the wafer block 206 in the desired position (referred to herein as a vacuum chuck). Further, a vacuum is also applied to the face of the wafer block 206 in contact with the rotating stop 215 via apertures or channels (not shown) in the rotating stop 215. As a result, the wafer block 206 is securely held in the desired position.

The slicing/grinding assembly 204 includes a spindle shaft 218 that rotates about axis 220. Both a slicing blade 216 and a grinding wheel 224 are mounted on the spindle shaft 218 and also rotate about the axis 220. The jig base 205 is moved into position in the z-direction and then moved in the x-direction to slice the wafer bar 230 from the wafer block 206. In another implementation, the jig base 205 remains stationary in the x-direction and/or the z-direction and the slicing/grinding assembly 204 moves into position in the z-direction and moves in the x-direction to slice the wafer bar 230 from the wafer block 206. In yet other implementations, both the jig base 205 and the slicing/grinding assembly 204 are capable of moving in the z-direction and/or the x-direction to slice the wafer bar 230 from the wafer block 206. The vacuum chuck applied to the wafer block 206 via the translation stage 208 keeps the wafer block 206 in the desired position during the slicing operation. The vacuum chuck applied to the wafer bar 230 via the rotating stop 215 keeps the wafer bar 230 in the desired position during the slicing operation.

FIG. 3 is a side view of an example dual-side wafer grinding apparatus 300 during a first grinding operation. The apparatus 300 includes a jig 302 and a slicing/grinding assembly 304. The jig 302 includes a jig base 305 used to orient a wafer block 306 with respect to the slicing/grinding assembly 304. A translation stage 308 is mounted on the jig base 305 and is moveable in the y-direction on rails (not shown) with precision (as illustrated by arrow 312). The translation stage 308 is used to move the wafer block 306 into and out of position for the slicing/grinding assembly 304 to accurately slice a wafer bar 330 from the wafer block 306 and grind the sliced surfaces of the wafer bar 330 and the wafer block 306. The slicing/grinding assembly 304 includes a spindle shaft 318 that rotates about axis 320. Both a slicing blade 316 and a grinding wheel 324 are mounted on the spindle shaft 318 and also rotate about the axis 320. The translation stage 308 is depicted in FIG. 3 in position for grinding operations of the wafer block 306.

Once the wafer bar 330 is sliced from the wafer block 306 (as illustrated in FIG. 2 and detailed description thereof), exact positions and/or dimensions of the wafer block 306 and wafer bar 330 may be accurately measured with inline measurement equipment (e.g., optical measuring devices, not shown). The jig 302 is moved away from the slicing/grinding assembly 304 in at least the x-direction and the translation stage 308 is repositioned in a grinding position by moving it in the negative y-direction as compared to the slicing position. The slicing/grinding assembly 304 is then moved in the positive y-direction to a precise position based on the measured positions and/or dimensions of the wafer block 306 and the wafer bar 330. The slicing/grinding assembly 304 is then moved in the negative z-direction to place the grinding wheel 324 between the wafer block 306 and the wafer bar 330. The jig 302 is then moved in the negative x-direction to grind the exposed surface 356 of the wafer block 306. In other implementations, the slicing/grinding assembly 304 is moved in the negative x-direction to grind the exposed surface 356 of the wafer block 306.

The apparatus 300 may include precision measuring equipment to measure the quantity and/or quality of grinding performed on the exposed surface 356 of the wafer block 306 and/or slicing of the wafer bar 330 from the wafer block 306. Further, the wafer block 306 and/or the wafer bar 330 may include alignment marks (not shown) to aid the measurement of the quantity and/or quality of the slicing and grinding operations. The quantity and/or quality of the slicing and grinding operations may be preset based on an average quantity and/or quality of the grinding and the slicing operations to achieve the desired edge straightness and/or overall dimensions of the wafer block 306 and the wafer bar 330. In other implementations, the quantity and/or quality of the slicing and grinding operations may be measured periodically or continuously as the grinding and the slicing operations are performed in order to achieve the desired flatness, perpendicularity, surface finish, and/or overall dimensions of the wafer block 306 and the wafer bar 330. The measurement results may be used for positioning the slicing/grinding assembly 304 for the next slicing/grinding operation. In one implementation, the ground wafer block 306 surface 356 is an air-bearing surface of a row of thin film heads diced from a next-in-sequence sliced wafer bar.

FIG. 4 is a side view of an example dual-side wafer grinding apparatus 400 during a second grinding operation. The apparatus 400 includes a jig 402 and a slicing/grinding assembly 404. The jig 402 includes a jig base 405 used to orient a wafer block 406 with respect to the slicing/grinding assembly 404. A translation stage 408 is mounted on the jig base 405 and is moveable in the y-direction on rails (not shown) with precision (as illustrated by arrow 412). The translation stage 408 is used to move the wafer block 406 into and out of position for the slicing/grinding assembly 404 to accurately slice a wafer bar 430 from the wafer block 406 and grind the sliced surfaces of the wafer bar 430 and the wafer block 406. The slicing/grinding assembly 404 includes a spindle shaft 418 that rotates about axis 420. Both a slicing blade 416 and a grinding wheel 424 are mounted on the spindle shaft 418 and also rotate about the axis 420. The translation stage 408 is depicted in FIG. 4 in position for grinding operations of the wafer bar 430.

Once the sliced surface 456 of the wafer block 406 has been ground (as illustrated in FIG. 3 and detailed description thereof), the slicing/grinding assembly 404 is moved in the positive y-direction to a precise position based on the measurement results discussed above with reference to FIG. 3 to grind the exposed surface of the wafer bar 430. In other implementations, the jig 402 is moved in the negative y-direction to grind the opposing exposed surface of the wafer bar 430.

The apparatus 400 may include precision measuring equipment to measure the quantity and/or quality of grinding performed on the exposed surface of the wafer bar 430 and/or slicing of the wafer bar 430 from the wafer block 406. Further, the wafer bar 430 may include alignment marks to aid the measurement of the quantity and/or quality of grinding performed on the wafer bar 430. The quantity and/or quality of grinding performed on the wafer bar 430 may be preset based on an average quantity and/or quality of grinding to achieve the desired edge straightness and/or overall dimensions of the sliced wafer bar 430. In other implementations, one or more of the edge straightness and/or overall dimensions of the sliced wafer bar 430 may be measured periodically or continuously as the grinding is performed on the wafer bar 430 in order to achieve the desired edge straightness and/or overall dimensions of the sliced wafer bar 430. The measurement results may be used for positioning the slicing/grinding assembly 404 for the next slicing/grinding operation. In one implementation, the ground wafer bar 430 surface is opposite the air-bearing surface of a row of thin film heads diced from the wafer bar 430.

Once both the wafer block 406 and the wafer bar 430 have been ground by the grinding wheel 424, the jig 402 is moved away from the slicing/grinding assembly 404, or vice versa. A rotating stop 415 rotates away from the wafer block 406 about shaft 426 (as illustrated by arrow 428). In one implementation, the rotating stop 415 rotates approximately 180 degrees about the shaft 426. The vacuum is released from the rotating stop 415 and the wafer bar 430 drops into a tray (not shown) for further processing. In implementations where gravity is insufficient to cause the wafer bar 430 to drop into the tray, a slight positive pressure may be applied to the vacuum apertures or channels in the rotating stop 415 to assist the release of the wafer bar 430 from the rotating stop 415.

The rotating stop 415 then rotates back into the position depicted in FIG. 4 (e.g., approximately 180 degrees from the position where the sliced wafer bar 430 is released from the rotating stop 415). In some implementations, the rotating stop 415 includes a locking mechanism to ensure that it remains in a desired position. A pusher (see e.g., pusher 112 of FIG. 1) is moved back in place and applies a y-direction force to move the wafer block 406 to a new desired position in contact with the rotating stop 415 and the aforementioned operations repeat to slice dual-side ground wafer bars from the wafer block 406 until the wafer block 406 is consumed or no additional wafer bars are desired.

FIG. 5 is a side view of an example dual-side wafer grinding apparatus 500 during a simultaneous dual grinding operation. The apparatus 500 includes a jig 502 and a slicing/grinding assembly 504. The jig 502 includes a jig base 505 used to orient a wafer block 506 with respect to the slicing/grinding assembly 504. A translation stage 508 is mounted on the jig base 505 and is moveable in the y-direction on rails (not shown) with precision (as illustrated by arrow 512). The translation stage 508 is used to move the wafer block 506 into and out of position for the slicing/grinding assembly 504 to accurately slice a wafer bar 530 from the wafer block 506 and grind the sliced surfaces of the wafer bar 530 and the wafer block 506. The slicing/grinding assembly 504 includes a spindle shaft 518 that rotates about axis 520. Both a slicing blade 516 and a grinding wheel 524 are mounted on the spindle shaft 518 and also rotate about the axis 520. The translation stage 508 is depicted in FIG. 5 in position for grinding operations of the wafer block 506 and wafer bar 530 simultaneously.

Once the wafer bar 530 is sliced from the wafer block 506 (as illustrated in FIG. 2 and detailed description thereof), the jig 502 is moved away from the slicing/grinding assembly 504 in at least the x-direction and the translation stage 508 is repositioned in a grinding position by moving it in the negative y-direction as compared to the slicing position. The grinding position depicted in FIG. 5 leaves a substantially smaller gap between the wafer bar 530 and the wafer block 506. More specifically, the gap between the wafer bar 530 and the wafer block 506 is equal to the thickness of the grinding wheel 524 plus the thickness of each of the wafer bar 530 and the wafer block 506 that is to be ground away (e.g., 4-10 mm). The gap may be verified using an inline measurement system (not shown) in conjunction with the alignment marks (not shown) on the wafer block 506 and/or wafer bar 530. The wafer block 506 position and/or the slicing/grinding assembly 504 position may then be finely adjusted based on the measurement results and wear factors of the grinding wheel 524. In order to effectively achieve the simultaneous dual grinding operation, the translation stage 508 is positioned with high accuracy (e.g., equal to or less than 0.1 μm error).

The corresponding gap depicted in FIGS. 3 and 4 is greater than the thickness of the grinding wheel 524 plus the thickness of each of the wafer bar 530 and the wafer block 506 that is to be ground away. In contrast to the simultaneous dual grinding operation, the separate grinding operations depicted in FIGS. 3 and 4 have a lower tolerance on the size of the corresponding gap (e.g., less than 10 μm error).

The grinding wheel 524 is drawn between the wafer block 506 and the wafer bar 530. The jig 502 is then moved toward the slicing/grinding assembly 504 in at least the x-direction, simultaneously grinding each of the sliced surface of the wafer block 506 and the sliced surface of the wafer bar 530. In other implementations, the slicing/grinding assembly 504 is moved in the x-direction to simultaneously grind each of the sliced surface of the wafer block 506 and the sliced surface of the wafer bar 530.

The apparatus 500 may include precision measuring equipment to measure the quantity and/or quality of grinding performed on the wafer block 506 and the wafer bar 530 and/or slicing of the wafer bar 530 from the wafer block 506. Further, the wafer block 506 and/or the wafer bar 530 may include alignment marks to aid the measurement of the quantity and/or quality of grinding performed on the wafer block 506 and/or the wafer bar 530. The quantity and/or quality of grinding performed on the wafer block 506 and/or the wafer bar 530 may be preset based on an average quantity of grinding to achieve the desired edge straightness and/or overall dimensions of the wafer block 506 and/or the wafer bar 530. In other implementations, one or more of the edge straightness and/or overall dimensions of the wafer block 506 and/or the wafer bar 530 ground surface may be measured periodically or continuously as the grinding is performed on the wafer block 506 and/or the wafer bar 530 in order to achieve the desired edge straightness and/or overall dimensions of the wafer block 506 and/or the wafer bar 530. The measurement results may be used for positioning the slicing/grinding assembly 504 for the next slicing/grinding operation. In one implementation, the ground wafer bar 530 surface is opposite the air-bearing surface of a row of thin film heads diced from the wafer bar 530.

Once both the wafer block 506 and the wafer bar 530 have been ground by the grinding wheel 524, the jig 502 is moved away from the slicing/grinding assembly 504, or vice versa. A rotating stop 515 rotates away from the wafer block 506 about shaft 526 (as illustrated by arrow 528). In one implementation, the rotating stop 515 rotates approximately 180 degrees about the shaft 526. The vacuum is released from the rotating stop 515 and the wafer bar 530 drops into a tray (not shown) for further processing. In implementations where gravity is insufficient to cause the wafer bar 530 to drop into the tray, a slight positive pressure may be applied to the vacuum apertures or channels in the rotating stop 515 to assist the release of the wafer bar 530 from the rotating stop 515.

The rotating stop 515 then rotates back into the position depicted in FIG. 5 (e.g., approximately 180 degrees from the position where the sliced wafer bar 530 is released from the rotating stop 515). In some implementations, the rotating stop 515 includes a locking mechanism to ensure that it remains in a desired position. A pusher (see e.g., pusher 112 of FIG. 1) is moved back in place and applies a y-direction force to move the wafer block 506 to a new desired position in contact with the rotating stop 515 and the aforementioned operations repeat to slice dual-side ground wafer bars from the wafer block 506 until the wafer block 506 is consumed or no additional wafer bars are desired.

FIG. 6 is a perspective view of a wafer block 606 and a dual-side ground wafer bar 630. The wafer bar 630 is sliced from the wafer block 606 (as illustrated by arrow 632) using apparatus 100 of FIG. 1 and/or operations 900 of FIG. 9, for example. In one implementation, the wafer block 606 is approximately 2.0″ wide (dimension 634), approximately 0.67″ long (dimension 636, prior to any wafer bar being removed from the wafer block 606), and approximately 850 μm thick (dimension 638). Further, the thickness of the wafer bar 630 sliced from the wafer block 606 may be less than 200 μm, or in some implementations less than 50 μm. Further, the wafer bar 630 has a consistent flatness, perpendicularity, surface finish, and overall dimensions as a result of the dual-side grinding operations performed on the wafer bar 630. Due to the extreme thinness of the wafer bar 630, the wafer bar 630 is referred to herein as having only two faces, each of which correspond to the surfaces that are sliced and ground in operations 900 of FIG. 9. In various implementations, each wafer block 606 will yield 20-40 wafer bars.

FIG. 7A is a partial cross-sectional view of a dual-side grinding wheel 724 with a rounded cutting surface 758. More specifically, FIG. 7A depicts a partial cross-sectional view of an edge of the grinding wheel 724 where the edge includes an area of increased thickness (referred to as a rounded cutting surface 758) about the outer circumference of the grinding wheel 724. The rounded cutting surface 758 may allow the grinding wheel 724 to remove material from a wafer block (not shown) and/or a wafer bar (not shown) while applying less stress on the wafer block and/or a wafer bar as compared to a grinding wheel with a consistent thickness from an inner radius to an outer radius.

In an example implementation, the total grinding wheel 724 diameter, illustrated by arrow 744, may range from 2.5″-4.0″. The wheel body thickness, illustrated by arrow 740, may range from 1.0 mm-12.0 mm. The rounded cutting surface 758 thickness, illustrated by arrow 742, may range from 2.0 mm-15.0 mm. A radius of curvature of the rounded cutting surface 758 may range from 2 mm-10 mm. A depth of the rounded cutting surface 758, illustrated by arrow 746, may range from 0.5 mm-4.0 mm.

FIG. 7B is a partial cross-sectional view of a dual-side grinding wheel 725 with a squared cutting surface 760. More specifically, FIG. 7B depicts a partial cross-sectional view of an edge of the grinding wheel 725 where the edge includes an area of increased thickness (referred to as a squared cutting surface 760) about the outer circumference of the grinding wheel 725. Similar to the rounded cutting surface 758 of FIG. 7A, the squared cutting surface 760 may allow the grinding wheel 725 to remove material from a wafer block (not shown) and/or a wafer bar (not shown) while applying less stress on the wafer block and/or a wafer bar as compared to a grinding wheel with a consistent thickness from an inner radius to an outer radius. However, the squared cutting surface 760 of FIG. 7B may apply more stress on the wafer block and/or a wafer bar than the rounded cutting surface 758 of FIG. 7A, but the squared cutting surface 760 may produce superior surface finish and/or flatness. Further, as the dual-side grinding wheel 724 of FIG. 7A is used, it may be worn down to a form resembling the dual-side grinding wheel 725 of FIG. 7B.

In an example implementation, the total grinding wheel 725 diameter, illustrated by arrow 748, may range from 2.5″-4.0″. The wheel body thickness, illustrated by arrow 750, may range from 1.0 mm-12.0 mm. The squared cutting surface 760 thickness, illustrated by arrow 752, may range from 2.0 mm-15.0 mm. A depth of the squared cutting surface 760, illustrated by arrow 754, may range from 0.5 mm-4.0 mm.

FIG. 8 is a front partial view of an example slicing/grinding assembly 804 with a dual-side wafer grinding wheel 824. The slicing/grinding assembly 804 includes an axle or spindle shaft 818 extending in the y-direction that may rotate as illustrated by arrow 822, or in the reverse direction. Both a slicing blade 816 and a grinding wheel 824 are mounted on the spindle shaft 818 and also rotate as illustrated by arrow 822, or in the reverse direction. The slicing blade 816 includes a blade holder 862 that securely holds blade 864. Further, the grinding wheel 824 includes an area of increased thickness 858 (see e.g., rounded cutting surface 758 of FIG. 7A and squared cutting surface 760 of FIG. 7B).

In one implementation, the slicing blade 816 is a diamond abrasive wheel and the grinding wheel 825 has a metal core with a metal-bonded diamond grinding surface. An outer diameter of the grinding wheel 824 is smaller than an outer diameter of the slicing blade 816 in order to prevent the grinding wheel 824 from contacting a corresponding dual-side wafer grinding apparatus (e.g., the apparatus 100 of FIG. 1) when the slicing blade 816 is being used. In other implementations, the outer diameter of the slicing blade 816 is smaller than an outer diameter of the grinding wheel 824.

Further, a wafer block or bar is depicted in a low grinding position 866 (solid lines) and a high grinding position 868 (dotted lines). The low grinding position 866 is defined by the lowest position where the wafer block or bar comes in contact with the entire area of increased thickness 858 of the grinding wheel 824. The high grinding position 868 is defined by the highest position where the wafer block or bar does not come in contact with the spindle shaft 818. The wafer block or bar may actually occupy any position between and including the low grinding position 866 and the high grinding position 868. Generally, the higher the wafer block or bar is positioned, the less contact area between the grinding wheel 824 and the wafer block or bar, which lowers grinding force on the wafer block or bar. However, the lower the wafer block or bar is positioned, the ground surface is generally flatter and smoother. In practice, the exact wafer bar position is defined by process requirements of the dual-side wafer grinding apparatus and resulting wafer bars.

FIG. 9 illustrates example operations 900 for operating a dual-side wafer grinding apparatus to manufacture wafer bars. In a first positioning operation 905, a thin film wafer block (e.g., a block of wafer material for manufacturing thin film magnetic heads) is secured in a jig at a desired position relative to a slicing/grinding assembly. The desired position is selected such that the slicing/grinding assembly may slice a desired thickness of substrate material from the wafer block.

In a slicing operation 910, a wafer bar of substrate material is sliced from the wafer block using the slicing blade of the slicing/grinding assembly. The wafer block remains secured in a translation stage of the jig. The sliced wafer bar remains secured to a rotating stop portion of the jig. In one implementation, the wafer block and the sliced wafer bar remain secured in place with vacuum chucks. In a second positioning operation 915, the wafer block is repositioned to allow dual-side grinding on the cut surfaces (or faces) of the wafer block and the wafer bar. More specifically, the wafer block is moved a sufficient distance away from the wafer bar to allow a grinding wheel of the slicing/grinding assembly to fit between the wafer block and the wafer bar.

In a first grinding operation 920, the sliced surface or face of the wafer block is ground down by contacting the grinding wheel with the cut surface or face of the wafer block. The first grinding operation 920 addresses variations in flatness, perpendicularity, surface finish, and/or overall dimensions of the cut surface or face of the wafer block, which in subsequent operations becomes a face of the next wafer bar sliced from the wafer block. In a second grinding operation 925, the sliced surface or face of the wafer bar is ground down by contacting the grinding wheel with the cut surface or face of the wafer bar. The second grinding operation 925 addresses variations in flatness, perpendicularity, surface finish, and/or overall dimensions of the cut surface or face of the wafer bar. In some implementations, the grinding operations 920, 925 are performed simultaneously. More specifically, if the second positioning operation 915 orients the wafer block a precise distance from the wafer bar equal to the grinding wheel thickness plus the desired removal of material from each of the wafer block and the wafer bar, the grinding operations 920, 925 can be performed simultaneously.

In a releasing operation 930, the rotating stop rotates away from the translation stage of the jig and the vacuum chuck on the wafer bar is released. The wafer bar falls into a tray and the rotating stop is returned to its original position. Further, the vacuum chuck on the wafer block is also released. The operations 900 repeat to sequentially slice dual-side ground wafer bars from the wafer bar until insufficient wafer bar material remains to slice a wafer bar therefrom.

The logical operations making up the embodiments of the invention described herein are referred to variously as operations, steps, objects, or modules. Furthermore, it should be understood that logical operations may be performed in any order, adding or omitting operations as desired, unless explicitly claimed otherwise or the claim language inherently necessitates a specific order.

The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Furthermore, structural features of the different embodiments may be combined in yet another embodiment without departing from the recited claims. 

What is claimed is:
 1. A method comprising: grinding opposing faces of a wafer bar sliced from a thin film wafer block.
 2. The method of claim 1, further comprising: slicing the wafer bar from the wafer block.
 3. The method of claim 2, wherein the grinding operation includes: grinding a first surface of the wafer block prior to the slicing operation; and grinding a second surface of the wafer bar after to the slicing operation, wherein the first surface and the second surface are the opposing faces.
 4. The method of claim 1, wherein the grinding operation is accomplished using opposite sides of a grinding wheel.
 5. The method of claim 4, wherein the grinding wheel has an area of increased thickness that performs the grinding operation.
 6. The method of claim 5, wherein the area of increased thickness has one of a curved cutting surface and a faceted cutting surface.
 7. The method of claim 1, wherein the grinding operation simultaneously grinds a face of the wafer block and a face of the wafer bar.
 8. The method of claim 1, wherein the grinding operation sequentially grinds a face of the wafer block and a face of the wafer bar.
 9. The method of claim 1, wherein the wafer bar includes a row of thin film heads.
 10. The method of claim 1, wherein the wafer bar is less than 200 μm thick.
 11. An apparatus comprising: a slicing blade mounted on an axle that slices wafer bars from a thin film wafer block; and a grinding wheel mounted on the axle that grinds opposing faces of the wafer bar.
 12. The apparatus of claim 11, wherein the grinding wheel is configured to grind a first surface of the wafer block prior to the slicing operation and grind a second surface of the wafer bar after to the slicing operation, wherein the first surface and the second surface are the opposing faces.
 13. The apparatus of claim 11, wherein the grinding wheel is configured to grind the opposing faces of the wafer bar using opposite sides of a grinding wheel.
 14. The apparatus of claim 11, wherein the grinding wheel has an area of increased thickness that performs the grinding operation.
 15. The apparatus of claim 14, wherein the area of increased thickness has one of a curved cutting surface and a faceted cutting surface.
 16. The apparatus of claim 11, wherein the grinding wheel is configured to simultaneously grind a face of the wafer block and a face of the wafer bar.
 17. The apparatus of claim 11, wherein the grinding wheel is configured to sequentially grind a face of the wafer block and a face of the wafer bar.
 18. The apparatus of claim 11, wherein the wafer bar includes a row of thin film heads.
 19. The apparatus of claim 11, wherein the wafer bar is less than 200 μm thick.
 20. A bar of thin film heads sliced from a block of substrate material, wherein the bar of thin film heads has mechanically ground opposing faces. 